IBinder的三个主要部分（暂不分析底层如何实现）

来源：互联网发布：手机本地端口1080 编辑：程序博客网时间：2024/06/05 00:19

1：定义服务类，如

AudioFlinger.cpp

MediaPlayerService.cpp

CameraService.cpp

AudioPolicyService.cpp

实现的过程参考前面的某一篇博客，差不多就是定义一个IXXXX，然后定义两个BnXXX和BpXXX等等；

2：在开机流程中，将这些服务注册到servicemanager中去，这个servicemanager有什么用涉及到IBinder的实现机制，暂不管，只要知道它是一个管理IBinder服务的地方，上面三个服务的注册在开机流程mediaserver这个最重要的继承创建后（Main_MediaServer.cpp）

int main(int argc, char** argv)

{

sp<ProcessState>proc(ProcessState::self());

sp<IServiceManager> sm =defaultServiceManager();

LOGI("ServiceManager:%p", sm.get());

AudioFlinger::instantiate();

MediaPlayerService::instantiate();

CameraService::instantiate();

AudioPolicyService::instantiate();

ProcessState::self()->startThreadPool();

IPCThreadState::self()->joinThreadPool();

}

具体每个服务类的instantiate(),大致一致，MediaPlayerService.cpp为例

void MediaPlayerService::instantiate() {

defaultServiceManager()->addService(

String16("media.player"), new MediaPlayerService());

}

其他几个只要换个名字就可以了：media.audio_flinger，media.audio_policy,media.camera

3：最后就是客户端需要使用这些服务的时候需要做的事情了：从servicemanager中取出相应的服务类的代理

代码基本一致，和上面一样只要换个名字就可以了

if (gAudioPolicyService.get() == 0) {

sp<IServiceManager> sm =defaultServiceManager();

sp<IBinder>binder;

do {

binder =sm->getService(String16("media.audio_policy"));

if (binder!= 0)

break;

LOGW("AudioPolicyService not published, waiting...");

usleep(500000); // 0.5 s

} while(true);

if (gAudioPolicyServiceClient == NULL) {

gAudioPolicyServiceClient = new AudioPolicyServiceClient();

}

binder->linkToDeath(gAudioPolicyServiceClient);

gAudioPolicyService =interface_cast<IAudioPolicyService>(binder);

gLock.unlock();

}

if (gAudioFlinger.get() == 0) {

sp<IServiceManager> sm =defaultServiceManager();

sp<IBinder>binder;

do {

binder =sm->getService(String16("media.audio_flinger"));

if (binder!= 0)

break;

LOGW("AudioFlinger not published, waiting...");

usleep(500000); // 0.5 s

} while(true);

if (gAudioFlingerClient == NULL) {

gAudioFlingerClient = new AudioFlingerClient();

} else {

if(gAudioErrorCallback) {

gAudioErrorCallback(NO_ERROR);

}

binder->linkToDeath(gAudioFlingerClient);

gAudioFlinger =interface_cast<IAudioFlinger>(binder);

gAudioFlinger->registerClient(gAudioFlingerClient);

}

if (sMediaPlayerService.get() == 0) {

sp<IServiceManager> sm =defaultServiceManager();

sp<IBinder>binder;

do {

binder =sm->getService(String16("media.player"));

if (binder!= 0) {

break;

}

LOGW("Media player service not published,waiting...");

usleep(500000); // 0.5 s

} while(true);

if (sDeathNotifier == NULL) {

sDeathNotifier = new DeathNotifier();

}

binder->linkToDeath(sDeathNotifier);

sMediaPlayerService =interface_cast<IMediaPlayerService>(binder);

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